1. Field of the Invention
This invention relates to a method and apparatus to change the program to be executed by a CPU in a multiprocessor system comprising a plurality of CPU's.
2. Description of the Prior Art
Conventionally, a multiprocessor system comprising a plurality of CPU's in its package is provided with a RAM or other storage means to store the program data to be executed for each CPU. To change program data in such a multiprocessor system, program data must be down loaded from outside to the plurality of CPU's. For this reason, a multiprocessor system having the first and the second CPU is provided with a storage means for data exchange between the two CPU's such as a dual port memory.
To change the program data, the first CPU receives the program data given from outside and changes the program data in its own RAM and at the same time uses the dual port memory RAM to pass the program data from outside to the second CPU. Then, the second CPU reads out the program data stored in the dual port memory RAM, and stores this program data to its own RAM in order to change the program.
However, in this conventional method for program change in a multiprocessor system, the first CPU is required to have not only a means to receive the program data from outside and change its own program, but also another means to pass the data to the second CPU. Further, the second CPU also requires a means to receive data from the first CPU. The need of several means to pass the program data from outside to each CPU and communication among them results in complicated processing for program change. Besides, a special storage means such as a dual port memory RAM is required for program data exchange among a plurality of CPU's.